A multi-component surrogate mechanism of diesel from indirect coal liquefaction for diesel engine combustion and emission simulations
A multi-component surrogate mechanism of diesel from indirect coal liquefaction for diesel engine combustion and emission simulations
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DOI：
10.1016/j.fuel.2022.123928
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发表时间：
2022-03-28
期刊：
影响因子：
7.4
通讯作者：
Huang, Haozhong
中科院分区：
文献类型：
--
作者：
Chen, Chunxia;Jia, Pengfei;Huang, Haozhong
煤炭间接液化柴油（DICL）是缓解过度依赖进口石油带来的石油安全问题、减少污染物排放的一种极具前景的替代燃料。然而，对煤间接液化柴油机理的研究却很少，对煤间接液化柴油燃烧和排放特性的数值模拟更是少之又少。因此，本工作提出了一种包含178个组分和650个反应的DICL简化机理，以研究不同负荷下DICL燃料的发动机的燃烧和排放特性。替代模型中，正十六烷（HXN）机理和2,2,4,4,6,8,8-七甲基壬烷（HMN）机理分别被认为是直链烷烃和支链烷烃的代表物种。首先，依次使用直接关系图和带有误差传播的直接关系图。然后，灵敏度分析与产率分析相结合，进一步简化了 2,2,4,4,6,8,8-七甲基壬烷机理的细节。之后，将正十六烷的骨架机理和还原的多环芳烃(PAH)机理与简化的HMN机理相结合，开发了一种新型的HXN-HMN-PAH多组分机理。分别在不同温度下进行蛮力敏感性分析，找出对点火延迟时间（IDT）影响较大的关键反应。然后，根据实验数据的点火延迟时间和详细机构对简化机构进行了优化。根据实际DICL的性能确定了71.5％HXN和28.5％HMN的摩尔分数比例。此外，采用优化的机制来验证实验值，包括点火延迟时间、喷射搅拌反应器（JSR）上的物质浓度和层流火焰速度。最终，将该机制耦合到计算流体动力学（CFD）中，在不同负载下的定向喷射压缩点火（DICI）发动机中进行多维数值模拟验证。
Diesel from indirect coal liquefaction (DICL) is a kind of extremely promising alternative fuel to alleviate the oil security problem caused by excessive dependence on imported oil and reduce the pollutant emission. However, the mechanism of diesel from indirect coal liquefaction is very few, and the numerical simulation of combustion and emission characteristics of diesel from indirect coal liquefaction is even less. Therefore, a reduced mecha-nism of DICL, entailing 178 components and 650 reactions, was put forward to research the combustion and emission characteristics of engines fueled with DICL under different loads in this work. n-Hexadecane (HXN) mechanism and 2,2,4,4,6,8,8-heptamethylnonane mechanism (HMN) were respectively considered as repre-sentative species of straight-chain paraffin and branched alkane in surrogate model. Firstly, direct relation graph and direct relation graph with error propagation were used in turn. Then, sensitivity analysis coupled with rate of production analysis has been used to further reduce the detail 2,2,4,4,6,8,8-heptamethylnonane mechanism. After that, the skeleton mechanism of n-hexadecane and the reduced polycyclic aromatic hydrocarbon (PAH) mechanism were combined with the simplified HMN mechanism to develop a novel multi-component mecha-nism of HXN-HMN-PAH. Brute-force sensitivity analyses were respectively conducted at different temperatures to find out these key reactions that have great effects on the ignition delay times (IDTs). Then, the optimizations of the reduced mechanism were made based on the ignition delay times of the experimental datum and the detail mechanism. A proportion of 71.5% HXN and 28.5% HMN by mole fraction was determined according to the properties of practical DICL. Furthermore, the optimized mechanism was employed to verify experimental values including the ignition delay times, the species concentrations on jet-stirred reactors (JSR) and the laminar flame speeds. Eventually, the mechanism was coupled into computational fluid dynamic (CFD) to perform multi-dimensional numerical simulation validation in a directed injection compression ignition (DICI) engine under different loads.